The present invention relates to a system having a VoIP (Voice over IP) function including a broadcasting function and a FAX (Facsimile) communication function based on a multicast that employs an IP (Internet Protocol) network.
FIG. 8 is a diagram showing an example of architecture of a conventional broadcast FAX transmission system. The FAX system shown in FIG. 8 actualizes, as follows, 1-to-n FAX communications between a transmitting (calling) terminal (FAX phone FA) and receiving (called) terminals (FAX phones FB (FB1, FB2, . . . , FBn; n is a natural number).
(1) 1-to-1 FAX communications are performed between the transmitting terminal (FAX phone FA) and a simultaneous broadcast FAX device EA via a notifying terminal A.
(2) 1-to-n FAX communications are performed between the simultaneous broadcast FAX device EA and a plurality of simultaneous broadcast FAX devices EB (EB1, EB2, . . . , EBn) via corresponding notifying terminals B (B1, B2, . . . , Bn).
(3) 1-to-1 FAX communications are performed between each simultaneous broadcast FAX device EB and the corresponding receiving terminal (FAX phone FB).
Operations shown in (1) and (3) given above are operations related to the normal FAX communications. By contrast, the operation in (2) is actualized by the simultaneous broadcast FAX device EA that separates and integrates the FAX information. The simultaneous broadcast FAX device EA separates pieces of information required for the FAX communications into signal information and data information. The separated data information has the following characteristics.
<1> The signal information is carried through bidirectional communications between transmitting/receiving sides of the data information, and involves confirming the transmission (acknowledgment of transmission). If unable to transmit the signal information, the communications are not established.
<2> The data information is carried through unidirectional communication from the transmitting side to the receiving side and does not involve confirming the transmission. If unable to transmit the data information, this causes only a deficiency of data but does not affect the communications on the whole.
A flow for actualizing the operation in (2) is given as follows.
[1] The simultaneous broadcast FAX device EA sets, by use of a phone function (phone control unit) possessed by a center device X, a signal information transfer path, one by one, between the respective simultaneous broadcast FAX devices EB1, EB2, . . . , EBn.
[2] When the signal information transfer paths for all the simultaneous broadcast FAX devices can be connected, the simultaneous broadcast FAX device EA flows, by use of a broadcasting function possessed by the center device X, the data information by broadcast.
[3] The data information distributed by the broadcasting function is received by the respective notifying terminals B1-Bn. The notifying terminals B1-Bn notify the corresponding simultaneous broadcast FAX devices EB1-EBn of the data information as voice information by use of external amplifier connecting terminals.
[4] The signal information transfer paths are released (disconnected) as triggered by completion of distributing the data information.
Each of the simultaneous broadcast FAX devices EB1-EBn has a bidirectional relay function. The simultaneous broadcast FAX devices EB1-EBn operate as below.
1) The simultaneous broadcast FAX device EB integrates the information sent in the form being separated into the signal information and the data information from the simultaneous broadcast FAX device EA, and sends the integrated information to the corresponding FAX phone FB.
2) The simultaneous broadcast FAX device EB sends transmission signal information from the FAX phone FB to the simultaneous broadcast FAX device EA via the signal information transfer path set in the actualization flow [1].
Note that a broadcasting system using the IP multicast is disclosed in Patent document 1 as the prior art related to the invention of the present application.
[Patent document 1] Japanese Patent Application Laid-Open Publication No. 2001-156847
The prior art given above has, however, the following problems.
First, the number of FAX recipients capable of receiving information distributed by the broadcast depends on ability to perform of the center device X including a simultaneous broadcast device, a phone control unit and a broadcasting control unit as shown in FIG. 8 and on the number of telephone lines.
Second, the simultaneous broadcast FAX device EA in the center device X and the simultaneous broadcast FAX device EB shown in FIG. 8 are high-cost and special devices that separate analog signals. Therefore, in the case of making modifications for enabling the IP-based communications to be performed between the center device X and the notifying terminals Bn, it is required that these devices are modified so that these devices support the IP.
Third, in the system shown in FIG. 8, between the center device X and the simultaneous broadcast FAX devices EBn, the normal phone connections are established and only the unidirectional data communications from the center to the receiving devices are conducted. Hence, it is difficult for the transmitting side to grasp which receiving device could actually receive FAX.